A Theoretical Study of the UV/Visible Absorption and Emission Solvatochromic Properties of Solvent‐Sensitive Dyes

Han, Wen Ge; Liu, Tiqing; Himo, Fahmi; Toutchkine, Alexei; Bashford, Donald; Hahn, Klaus M.; Noodleman, Louis

doi:10.1002/cphc.200300801

Cited by 98 publications

(82 citation statements)

References 30 publications

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“…The nonequilibrium PCM model used is a good approximation for nonpolar solvents that are not involved in site-specific interaction with solute molecules (36)(37)(38). The scatter diagram of β vec -BLA parameter and a plot of hβ vec ðBLAÞi against the BLA parameter are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Breakdown of the first hyperpolarizability/bond-length alternation parameter relationship

Murugan

Kongsted

Rinkevičius

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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We have investigated the dependence of the static first hyperpolarizability on the bond-length alternation (BLA) parameter. Our analysis indicates that the validity of the first hyperpolarizability/BLA parameter relationship is restricted to the no-field, vacuum, limit, while it successively breaks down along with increasing polarity of a surrounding medium, becoming invalid, for instance, in an aqueous solution. This contention is based on a series of TD-DFT, TD-DFT/PCM and hybrid TD-DFT/MM calculations of the first hyperpolarizability for a set of molecular configurations generated from Car-Parrinello hybrid QM/MM simulations of the stilbazolium merocyanine chromophore in chloroform and water solvents, and on a rationalization by means of the two-state model for the first hyperpolarizability. The BLA dependence of the three parameters entering the two-state model is shown to be qualitatively different in vacuum and in solvents. Particularly, in the vacuum case, the difference between ground and excited state dipole moments goes to zero for a vanishing BLA, which is not true in the presence of an aqueous medium. In the aqueous medium, an opposing behavior of the parameters involved in the two-state model results in an almost constant first hyperpolarizability with varying BLA parameter.bond-length alternation | hybrid QMMM modeling | nonlinear optical materials S implifying thumb rules and structure-property relations are of utmost significance in rational design of new materials with prespecified properties. Computational modeling plays an important role in that context because it can provide accurate number prediction of the property in question and can elucidate the merits and limitations of the simplifying thumb rules and so make their utility more precise (1). We find good evidence of this in the research of nonlinear optical (NLO) materials, where several structure-property relations are highlighted (2-12) and where computational modeling has advanced quite far (13). One such important structure-property relation for NLO materials is the relation between the first hyperpolarizability and the bond-length alternation (BLA) parameter for molecules that can exist in resonance between the two, neutral or charge-separated (zwitterionic) forms (2-12). The BLA parameter has been defined as the difference between the average single and double bond lengths in the conjugation pathway (14). By convention, it has been defined to be positive for the neutral form of a molecule while it takes negative values for the charge-separated form. Many theoretical studies have been performed with the purpose of investigating the effect of electric fields and solvents in altering BLA (9, 14-16). It has been shown that with increasing field strength and increasing solvent polarity, the BLA parameter decreases and in some cases changes sign with a cyanine-like structure corresponding to a BLA parameter equal to zero (14, 17). The BLA parameter has therefore been proposed to be a structural parameter to be tuned for optimizing nonlin...

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Section: Resultsmentioning

confidence: 99%

Breakdown of the first hyperpolarizability/bond-length alternation parameter relationship

Murugan

Kongsted

Rinkevičius

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…[1][2][3] These shifts are caused by a different stabilization of ground and excited states by the solvent within the Franck-Condon region, i.e., without a reorientation of the solvent molecules upon absorption or emission. In recent time, several attempts have been made to model the solvatochromic shifts of simple compounds such as acetone, 4,5 triazines or tetrazines, [6][7][8] solvatochromic organic dyes, [9][10][11] or transition metal compounds [12][13][14][15] with different explicit or implicit models for the solvent.…”

Section: Introductionmentioning

confidence: 99%

The merits of the frozen-density embedding scheme to model solvatochromic shifts

Neugebauer

Louwerse

Baerends

et al. 2005

The Journal of Chemical Physics

235

373

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We investigate the usefulness of a frozen-density embedding scheme within density-functional theory ͓J. Phys. Chem. 97, 8050 ͑1993͔͒ for the calculation of solvatochromic shifts. The frozen-density calculations, particularly of excitation energies have two clear advantages over the standard supermolecule calculations: ͑i͒ calculations for much larger systems are feasible, since the time-consuming time-dependent density functional theory ͑TDDFT͒ part is carried out in a limited molecular orbital space, while the effect of the surroundings is still included at a quantum mechanical level. This allows a large number of solvent molecules to be included and thus affords both specific and nonspecific solvent effects to be modeled. ͑ii͒ Only excitations of the system of interest, i.e., the selected embedded system, are calculated. This allows an easy analysis and interpretation of the results. In TDDFT calculations, it avoids unphysical results introduced by spurious mixings with the artificially too low charge-transfer excitations which are an artifact of the adiabatic local-density approximation or generalized gradient approximation exchange-correlation kernels currently used. The performance of the frozen-density embedding method is tested for the well-studied solvatochromic properties of the n → * excitation of acetone. Further enhancement of the efficiency is studied by constructing approximate solvent densities, e.g., from a superposition of densities of individual solvent molecules. This is demonstrated for systems with up to 802 atoms. To obtain a realistic modeling of the absorption spectra of solvated molecules, including the effect of the solvent motions, we combine the embedding scheme with classical molecular dynamics ͑MD͒ and Car-Parrinello MD simulations to obtain snapshots of the solute and its solvent environment, for which then excitation energies are calculated. The frozen-density embedding yields estimated solvent shifts in the range of 0.20-0.26 eV, in good agreement with experimental values of between 0.19 and 0.21 eV.

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“…The ΔSCF procedure of DFT method normally under-estimates the absolute value of the S 1 state energy, and therefore also the vertical excitation energy. 19,20 However, the directions and approximate magnitudes of the solvatochromic shift are correctly predicted.…”

Section: Absorption Spectramentioning

confidence: 88%

Experimental and DFT Studies: Novel Structural Modifications Greatly Enhance the Solvent Sensitivity of Live Cell Imaging Dyes

et al. 2007

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Structural modifications of previously reported merocyanine dyes (J. Am. Chem. Soc. 2003, 125, 4132-4145) were found to greatly enhance the solvent dependence of their absorbance and fluorescence emission maxima. Density functional theory (DFT) calculations have been performed to understand the differences in optical properties between the new and previously synthesized dyes. Absorption and emission energies were calculated for several new dyes using DFT vertical self-consistent reaction field methods (VSCRF). Geometries of ground and excited states were optimized with a Conductor-like screening model (COSMO) and self-consistent-field (SCF) methods. The new dyes have enhanced zwitterionic character in the ground state, and much lower polarity in the excited state, as shown by the DFT-VSCRF calculations. Consistently, the position of the absorption bands are strongly blue-shifted in more polar solvent (methanol compared to benzene) as predicted by the DFT spectral calculations. Inclusion of explicit H-bonding solvent molecules within the quantum model further enhances the predicted shifts, and is consistent with the observed spectral broadening. Smaller, but significant spectral shifts in polar versus nonpolar solvent are predicted and observed for emission bands. The new dyes show large fluorescence quantum yields in polar hydrogen bonding solvents; qualitatively, the longest bonds along the conjugated chain at the excited S 1 state minimum are shorter in the more polar solvent, inhibiting photoisomerization. The loss of photostability of the dyes is a consequence of the reaction with and electron transfer to singlet oxygen, starting oxidative dye cleavage. The calculated vertical ionization potentials of three dyes I-SO, AI-SO(4), and AI-BA(4) in benzene and methanol are consistent with their relative photobleaching rates; the charge distributions along the conjugated chains for the three dyes are similarly predictive of higher reaction rates for AI-SO(4) and AI-* Corresponding authors. khahn@med.unc.edu, lou@scripps.edu. 2 These authors contributed equally to this work. Supporting InformationThe Cartesian coordinates of the S 0 and S 1 state COSMO optimized dye structures, and more detailed atomic ESP charges of the S 0 state dye molecules in MeOH are given in the Supporting Information. BA(4) than for I-SO. Time dependent DFT (TDDFT) calculations were also performed on AI-BA(4); these were less accurate than the VSCRF method in predicting the absorption energy shift from benzene (C 6 H 6 ) to methanol (MeOH). NIH Public Access

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A Theoretical Study of the UV/Visible Absorption and Emission Solvatochromic Properties of Solvent‐Sensitive Dyes

Cited by 98 publications

References 30 publications

Breakdown of the first hyperpolarizability/bond-length alternation parameter relationship

Breakdown of the first hyperpolarizability/bond-length alternation parameter relationship

The merits of the frozen-density embedding scheme to model solvatochromic shifts

Experimental and DFT Studies: Novel Structural Modifications Greatly Enhance the Solvent Sensitivity of Live Cell Imaging Dyes

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